The invention relates to an adhesive activated polyester fibrous material. More specifically, the invention relates to a polyester fibrous material for incorporation into rubber.
Polyester fibers, cords and fabrics are used extensively for reinforcing rubber articles such as tires, belts, hoses and the like. But, polyester textile elements generally adhere poorly to rubber unless first treated to improve adhesion, as by coating. Because of the exceptional strength and reinforcing ability of polyester fibers there has been a continuous effort to improve the adhesion of polyesters to rubber.
A widely used process for adhering polyester to rubber involves coating polyester with an RFL latex which contains a resorcinolformaldehyde resin. The thus coated polyester is heated and then incorporated into rubber. But, the system can be unsatisfactory depending on factors such as the degree of polyester heat treatment; the composition of polyester substrate; the amount of stress and heat the reinforced rubber article undergoes; and the like.
In order to further improve polyester adhesion, polyester fibers are typically coated during spinning with an adhesive activator. In actual commercial practice, such adhesive activators, as a general rule, comprise one or more active epoxy compounds. Notable are compounds such as dimethylol-bisphenol-A-diepoxide, butanediol diglycidic ether, glycerol diglycidyl ether and epoxidized silanes. Such epoxy compounds have been found to greatly increase adhesion of polyester to rubber when used prior the RFL dip.
Nevertheless, an extensive search has been made for different adhesive activating agents for bonding polyester to rubber. An epoxy replacement would be highly desirable because of indications that the epoxies present hazards to humans involved in spinning. Though the search for an epoxy substitute has been ongoing for several years, few compositions capable of matching the performance of epoxies have emerged.
There is therefore a need for an alternative adhesive activating system which can replace the epoxy spin finish while achieving adhesive results substantially the same to the epoxy. Any such candidate should fit into existing fiber producing procedures and be compatible with the RFL dip systems widely used by rubber article manufacturers.